One benefit of a rechargeable battery is that a user does not need to worry about an unexpected power out of the electrical device being used. Further, the rechargeable battery has the advantages of being portable, reusable, convenient in use, and environment friendly. Hence, rechargeable batteries are widely used in many applications due to the significant increase of capacity and technological advancements of charge materials. For example, a rechargeable battery has been installed in a small home appliance (e.g., stereo). More recently, how to equip a motor vehicle (e.g., motorcycle or car) with one or more rechargeable batteries for making it battery operated has become more important. Hence, it is critical to correctly measure the quantity of electricity of a rechargeable battery.
R.O.C. Patent Publication No. 507,412 entitled “Rechargeable Battery Charger, Method of Charging A Rechargeable Battery, and Rechargeable Battery Assembly” disclosed a rechargeable battery charger for charging batteries of a rechargeable battery assembly. The rechargeable battery assembly is able to record data of the maximum charge current of the batteries and data of the maximum charge voltage of the batteries, and has means of communicating data and a memory of storing digital data representing the maximum charge voltage. Another R.O.C. Patent Publication No. 522,624 entitled “Rechargeable Battery Charger, Rechargeable Battery Assembly, And Method of Secondarily Charging The Rechargeable Battery” disclosed a small charger adapted to charge a number of rechargeable batteries in a reduced period of time.
The above two charge methods have fully disclosed techniques of how to effectively charge one or more rechargeable batteries in a minimum period of time. However, for a user it is more important to know the actual quantity of electricity of a rechargeable battery prior to use. Thereafter, the user is able to determine about when he/she will charge the battery again or replace it with a new one after using it for a period of time in the future. A further R.O.C. Patent Publication No. 533,646 entitled “Rechargeable Battery Charging System and Rechargeable Battery Charger Thereof” disclosed a microcontroller employing an algorithm to monitor the charge state of rechargeable battery and generate a control signal therefor, and supply optimum voltage and current to charge the rechargeable battery. The patent has a feature of measuring the quantity of electricity of the rechargeable battery. However, there is only one measurement of determining whether the rechargeable battery is charged or not. In fact, the patent does not teach how to measure the actual quantity of electricity of a rechargeable battery being charged.
In view of the above, it is understood that the prior art is able to only determine whether a rechargeable battery is fully charged or not. This feature does not help too much for most users. For example, for driving a battery operated motorcycle, there is no way for the driver to know a maximum distance that the vehicle can travel in one charge since the driver does not know the actual quantity of electricity stored in the rechargeable battery. Further, there is no way for the driver to know the charge time. These problems really bother users.
In addition, the conventional technique of measuring the actual quantity of electricity of a rechargeable battery involves measuring the battery directly during charge. However, the measured actual quantity of electricity of the battery being charged may be not the actual quantity of electricity thereof since the battery is being charged by an external power source. Hence, it is typical that the measurement is higher than the actual quantity of electricity of the battery. In other words, the measurement is not correct. This in turn may cause an incorrect determination of the actual quantity of electricity of a rechargeable battery being charged by a user. Hence, a need for improvement exists.